Resistor molding apparatus



Sept. 11, 1934. H, SKLAR y 1,973,117

RESISTOR MOLDING APPARATUS Original Filed April 17, 1935 2 Sheets-Shea?l y h INVENTOR ATTOR EYS' v rna/ vtm@ sept. 11, 1934. H; L SKLAR v 1,973,117

RESISTOR MOLDING APPARATUS original Filed April 17, 1933 2 sheets-'shea 2 /l 16 17 Z0 8 Z1 .19 19 A1-TOR EYs Patented Sept. 11, 1934 entre srrss RESISTOR MLDING APPARATUS Herman L. Sklar, Coney Island, N. Y., assignor to Micamold Radio Corporation, Brooklyn, N. Y., a corporation of New York Original application April 17, 1933, `Serial No.

Divided and this application October 6, 1933, Serial No. 692,407

5 Claims. (Cl. 18-5) The invention relates to thel manufacture of electrical resistors wherein the terminals of the resistor are embedded within a mass of resistance material, and aims primarily to provide apparatus 5 by which resistors of the above character may be economically and rapidly produced in large quantities. Certain of the features of the invention are particularly applicable to hot molded resistors, while others are also applicable to cold molding processes, as hereinafter explained in greater detail in the following specification which, taken in conjunction with the accompanying drawings, illustrates an apparatus adapted to be used in forming resistors in accordance with the invention, and certain steps or stages in such manufacture. In

' the drawings- Fig. 1 showsa plurality of resistor terminals carried by a supporting and positioning strip adapted to be used as a part of the present invention.

' Fig. V2 is a view similar to Fig. 1 but showing the kterminals projecting toward the right of the figure coated with a low resistance material, which may be used to facilitate good electrical contact between the terminals and the resistance material proper. g

Fig. 3 is a plan view of a resistor terminal supporting frame adapted to be used in carrying out the present invention, to support terminal holding strips of the character shown in Figs. 1 and'2, a portion of one of the plates forming part of such frame being cut away.

Fig. 4 is a bottom plan View of an upper main molding die adapted to be used in carrying out the invention, and indicating in dotted lines the operative position of the above mentioned frame in respect to such die.

Fig. 5 is a sectional View through said frame taken onthe broken line 5-5 of Fig. 3, looking in the direction of the arrows.

Fig. 6 is a plan view of a main molding die adapted to be used in carrying out the invention. Fig. 7 is a sectional View through a pair of main molding dies, with the resistor terminal carrying frame in operative position therebetween, and illustrating the position of the parts at the beginning of the molding operation.

Fig. 8 `is a View similar to Fig. '7 but showing the position of the parts at the completion of the molding operation. Fig. 9 is a fragmentary sectional view taken on line 9 9 of Fig. 8 looking in the direction of the arrows. Y f

Fig. 10 'isa klongitudinal sectional View of a completed resistor unit.v

. use is desired.

The invention is illustrated as applied to the manufacture ci electrical resistor units of the type illustratedin Fig. 1,0, having a main body portion of suitable resistance material 1 which may be of any suitable composition, for example, such as is known in the art having graphite, carbon black and iron oxide serving as conducting material, with a small percentage of high melting point Wax, together with a binder consisting of phenol formaldehyde, resin and asbestos or other suitable inert filler. Various compositions suitable for the above purposes are well known in the art.

Wire terminals 2 are embedded within the resistance material 1 and usually project from the opposite ends thereof as shown in Fig-10; preferably the terminals 2 are provided with enlarged heads 3 and I prefer also to provide the embedded ends of the terminals with a low resistance coating 4 in order to insure a noiseless Contact between the terminal 2 andthe main body 1 of the resistor. The low resistance coating 4 may be, for example, of a composition vsimilar to the main bodyv portion 1 of the resistor, but with an increased percentage of conducting material therein,.or an alloy of low melting point may be employed, or a composition containing graphite and ansu'itable binder. y v

In forming resistors according to the invention in its preferred form, a series of resistor terminals ,2 are placed in properly positioned alined recesses in a supporting strip 5 of tapelike character as indicated in Fig. 1, the heads 3` of the terminals projecting out sidewise from; the strip. This strip 5 if desired may be'of paper and may support the terminals in a manner similar to that employed for supporting pointed pins in common use, or a metal strip may be employed where a terminal support-suitable for repeated Tape-like strips of the above character, carrying the terminals in proper position, may readily be obtained orproduced in long lengths, usually inv coil or roll; form from which the desired lengths ofv strip may becut off.

While the resistor terminals are supported as' above described, their ends 3 may be readily coated to form the low resisting coating 4, as indicated at the right of Fig. 2, for example by dipping the ends of the terminals in a low resistance composition while properly supported by strip 5, or spraying the composition thereon. With a large number of terminalsso accurately positioned and supported, the coatingfmayv bey appliedmuch-Ymore rapidly*and accurately.

provided grooves 9 adapted to receive the terminals 2, when the strips 5 are placed in proper position between dies 6 and 7.

I prefer to employ in connection with the strips 5 a holding frame of the character shown in Figs. 3 to 5, which is interposed between the main dies 6 and 7 during the molding operation. This holding frame may consist of a pair of plate-like members 10 and 11 detachably iitting together in definite relationship, dowel pins 12 in plate 11 being shown in Fig. 5 for this purpose, and fitting inV holes 13 in plate 10. The strips 5 may also be provided with holes 14 engaging pins 12, which locate the resistor terminals 2 accurately in respect tothe holding frame, and the holding fra-me in turn may be accurately located in respect to the main dies 6 and 7, as by means of the holes 15 in the plates 10 and 11. which engage with the dowel pins 16 shown in Fig. 7 as mounted on the main die 7 and passing into dowel holes 17 in the lower main die 6.

In the illustrated form of the invention the plates Y10 and 11 of the terminal holding frame are provided with openings 18, which line up with the resistor shaped recesses 8 when the holding frame is placed in operative position, the walls of the plates adjacent said openings 18 serving to hold the terminals 2 and their supporting strips 5 securely in position. The opposed walls of the main dies 6 and 7 are provided with interior depressed portions 19 and marginal depressed portions 20 adapted to receive the holding frame constituted bythe plates 10 and 11, when the dies are forced together into the position rshown in Fig. 8. This construction of the dies 6 and 7 leaves lands 21 surrounding the resistor-shaped recesses 8, and the terminal receiving grooves 9 are formed in these lands.

Preferably the holding frame comprised of plates 10 and 11, and the terminal supporting strip'fare used in conjunction'as above described, for vthe purpose of properly and securely positioning the resistor terminals in the mold, but it should be noted that the strips' may be employed alone for theabove purposes, although when used conjointly with the frame they will better insure that the terminal strands are properly held and afford greater facility in handling.

In forming resistors occording to the present invention a plurality of pills or blocks 22 (Fig. 8) of suitable resistance material may be first placed in recesses 8 of main die 6, suitable means for rapidly performing such an operation 'being known in the art and accordingly not described in detail herein. A suitable number of Aterminal supporting strips 5 (the heads 3 thereof being preferably first coated with a suitable material 4), will then be placed in engagement with the dowels 12 of plate 11 of the holding frame. In the use of the illustrated forms of main dies 6 and 7, it will be noted that the terminal strip 5 4 shownrin Fig. 1, containing only a single series of terminals projecting from'one-side thereof, is suitable for use atthe opposite side edges of the main dies, while the supporting'strip 5 shown in Fig. 2, which is provided with two series of resistorterminals in staggered *relation and 'with their ends projecting from opposite sides of the strip, is suitable for positioning in the intermediate recessed portions 19 of the main dies, one such strip 5 thereby serving both rows of resistor shaped recesses which are located on opposite sides thereof. f

After the strips 5 have been properly positioned on plate 11 as above described, the plate 10 may berplaced in proper relation to the plate 11 and the resistor terminal holding frame thereby constituted may be placed in proper position relative to the main dies 6 and 7, by engagement of holes 15 in the holding frame with dowels 16 of main die 7. In the illustrated form of the invention screws 23 (Figs. 3, 5 and 9) pass through the plate 10 ofthe 'hol/ding frame and holes 24 in plate 11 into the main die 7 thereby detachably connecting the terminal holding frame to main die 7.

Iheillustrated die construction is adapted to be used in a hot molding process, the dies 6 and 7 being heated in such manner that the pills or blocks 22 of resistance material are quickly softened when placed in position, the result being that when pressure is Vapplied VVto `force the dies together from the position shown inFig. 7 to that of Fig. 8, the resistance material 1 readily ows lin recess -8 in such manner as to completely surround vthe heads 3 of terminals 2, and embed the latter therein. It `should* be understood, however, that many of the'feat-ures -oi the invention are also applicable to cold molding processes. The hot molding process,U however, produces a resistor having a glaze which affords asubstantially moisture impervious surface.

After the molding operationhasbeen completed and main dies 6 and 7 separated, vthe holding frame constituted by plates 110 and 1-1 carrying the completed resistor units may bedetached from die 7, and plates 1-0 andA 1`1 separated to allow removal therefrom of the completed resistor units, which vare vvthen supported -by the strips'. vSubsequent handling of the resistors `is much facilitated by having aX large number 'o'f them supported inthe above manner. v This application is a ldivision 'of' my prior application Serial Number 666,415, iiled April 1-7, 1933 entitled Method of and apparatus for forming resistors. Y

While a specic apparatus Vand 'mode of Y'procedurefha've -been described above, it should be understood that many changesmay bejmade therein without departing -'from ythe essentials of l:the invention as set forth in the appended claims.

I claim:

1. A molding apparatus of the-class described, including mating main dies Adefining a rowl of resistor-shaped*recesses, 'and tape-'like strips interposed between said dies and respectively disposed along opposite sides vof said row, :each of said tape-like strips having means spaced along the length Athereof for supporting a plurality of resistor terminals in position to project laterally therefrom vinto the respectively adjacent -rl'ecesses of thedies.

2. A molding-apparatus of the class` described, including mating main dies defining -a row of resistor-shaped recesses, aresistor'te'rminal holding frame detachable from and `adapted tov t between said dies, said frame comprising separableplates having openings therein adapted to line upwithsaid'row of recesses andzsaidframe being provided with means adapted to hold iresister terminals in nposition between #said i" plates with their ends projecting mtosaidfrecesses.

Ill)

3. A molding apparatus of the class described, including mating main dies defining a row of resistor-shaped recesses, a resistor terminal holding frame detachable from and adapted to iit between said dies, said frame comprising separable plates having openings therein adapted to line up with said row of recesses and tapelike strips located between said plates having means spaced along the length thereof for supporting a plurality of resistor terminals in position to project laterally therefrom into the respectively adjacent recesses of the dies.

4. A molding apparatus of the class described including mating main dies dening a plurality of spaced rows of resistor-shaped recesses, and tape-like strips interposed between said dies and respectively disposed between said rows of recesses and along the outer sides of the outer rows of said recesses, each of said tape-like strips having means spaced along the length thereof for supporting a plurality of resistor terminals in position to project laterally therefrom into the respectively adjacent recesses of the dies.

5. A molding apparatus of the class described including mating main dies defining a plurality of spaced rows of resistor-shaped recesses, a resistor terminal holding frame detachable from and adapted to fit between said dies, said frame having openings therein adapted to line up with said rows of recesses, and a plurality of tapelike strips each engaging said frame and positioneol between said rows of recesses and also along the outer side of the outer rows of said recesses, each of said tape-like strips having means spaced along the length thereof for supporting a plurality of resistor terminals in position to project laterally therefrom into the respectively adjacent recesses of the dies.

HERMAN SKLAR. 

